The general objective of this proposal is the immunogenetic analysis of cellular alloantigen systems in the mouse. This will include a continued effort to define the fine structure of the H-2 gene complex by recombinational analysis, to prepare congenic lines bearing new recombinant chromosomes, to fully characterize the recombinants in collaboration with other investigators, to use the recombinant lines to prepare more highly specific serological reagents and to make the recombinant lines and reagents available to investigators who have a legitimate use for them. It is also planned to continue the study of the immunogenetic inter-relationships of cellular alloantigen systems, especially those that involve genetically regulated immune responses to alloantigens.